Speed Control Behavior of Drivers in High-Density Interchange Groups: Considering the Effects of Interchange Spacing, Driving Conditions, and Driver Heterogeneity

High-density interchange groups (HDIG) have become an increasingly common feature in urban transport infrastructure, but the reduction of the spacing between interchanges has led to poor weaving environments and disorganized traffic flows. However, this safety issue has not yet attracted much attention. This study aims to investigate the effects of interchange spacing, driving conditions, and driver heterogeneity on the speed control behavior of drivers in HDIGs. A naturalistic driving test was carried out at an HDIG in Chongqing, China, where real-vehicle operating data were collected from 37 drivers, and the effects of their interactions with driving conditions, driver gender, and driving style on vehicle longitudinal speed and acceleration were discussed separately, using the spacing of the interchanges as the key factor. The drivers’ speed control patterns varied under different interchange spacing, especially under ramp-to-mainline conditions, where vehicle travel speed and driving stability were more significantly affected by interchange spacing and driver heterogeneity. In addition, the driving behaviors of drivers of different genders and styles were found to differ to some extent, and the driving conditions affected the significance of the differences. This study reveals the effects of interchange spacing, driving conditions, and driver heterogeneity on speed control behavior in HDIGs, discusses further the possible reasons for the differences in driving behavior, and proposes targeted improvement measures. Moreover, this study provides theoretical support for the development of design specifications for HDIGs in urban and traffic safety management measures to reduce the number of traffic accidents at the interchange.